Method and apparatus for loading fuel rods into a container

ABSTRACT

A method and an apparatus for loading containers with individual fuel rodsr fuel-rod sections of irradiated nuclear reactor fuel elements are disclosed. In order to ensure maximum safety, cleanliness and close packing when loading the containers, the fuel rods or fuel-rod sections are horizontally front-loaded into the container which is horizontally positioned. The loading aperture is located as closely as possible to the upper inner periphery of the container. Following their insertion, the fuel rods or fuel-rod sections will drop onto the inner wall surface of the container or onto the already existing pile of previously loaded fuel rods or fuel-rod sections. The container for loading with such a method has a loading aperture in the end wall thereof arranged close to the inner periphery thereof for insertion of the fuel rods or fuel-rod sections. The apparatus for loading containers in accordance with the method disclosed includes a loading trough which is insertable into a loading aperture in the container and serves to load the fuel rods or fuel-rod sections. The loading trough is capable of being rotated about its longitudinal axis whereupon the fuel rod or fuel-rod section drops down.

FIELD OF THE INVENTION

The invention relates to a method and apparatus for loading a containerwith separated fuel rods or with cut fuel-rod sections of irradiatednuclear reactor fuel elements. A container for receiving the irradiatedmaterial is also disclosed.

BACKGROUND OF THE INVENTION

It has been proposed to handle the direct terminal storage of fuelelements such that the fuel elements are disassembled and the individualfuel rods are then placed in terminal storage containers more closelypacked than was previously possible. This close packing of the fuel rodshas the advantage that a larger number of fuel elements can beaccommodated in a terminal storage container.

Further, it has been proposed to cut up the individual fuel rods intosections and then load the same into the containers provided. Thispermits smaller storage unit sizes for direct terminal storage. Incontrast to terminal storage containers filled with whole fuel rods,this would afford the advantage of permitting the handling of terminalstorage containers of shorter lengths and lower weights in the terminalstorage mining depot.

Further, this method makes it possible to use storage unit sizes thedimensions of which correspond to the terminal storage cans of highlyactive waste glass. In the mining depot, this would have the advantagethat only one storage unit size for highly active waste has to behandled.

When separating the fuel rods from the fuel element or when cutting upfuel rods and loading them into a container, the problem arises that theoutside of the container becomes contaminated by the radioactive cellatmosphere. Further, it is desirable to pack the fuel rods or fuel-rodsections as closely as possible in order to make optimum use of thestorage space.

SUMMARY OF THE INVENTION

It is an object of the invention to provide the above-mentioned typewhich permits a safe, clean and dense loading of the containers.

The fuel rods or cut up sections thereof are front-loaded into thecontainer in horizontal position. Since this takes place close to theupper inner periphery of the container, the container can be optimallyloaded with the fuel rods or fuel-rod sections. The method of theinvention requires only a small loading aperture in the container endwall. If the loading aperture is to be welded in a conditioning facilityafter loading, this small aperture represents still another advantage.

In another advantageous embodiment of the invention, the inner chamberof the container is subjected to a partial vacuum during loading, withthe extracted air being conducted through a filter prior to leaving thecontainer. By virtue of this method, dust developed during theseparation of the fuel rods from the fuel element or when cutting thefuel rods can be drawn directly into the container after the separatingor cutting facility is connected to the vacuum air system. Aerosols andfuel particles remain almost completely in the container into which thefuel rods or fuel-rod sections are loaded.

In an advantageous improvement of the invention, the container is loadedin a work chamber which is separate from the chamber in which the fuelrods are separated, cut up or supplied. This prevents contamination ofthe container to be loaded.

The invention also relates to a container to be loaded with fuel rods orfuel-rod sections according to the method of the invention. Thecontainer to be loaded has two closed small-diameter bores in its endwall. The two bores define an opening for loading and for the dischargeof air, respectively. The fuel rods or fuel-rod sections are introducedthrough the loading opening. Via the air discharge opening, thecontainer may be connected with a vacuum source whereby a drop inpressure from the outside to the container interior develops, so thatthe material held in the container cannot constitute a risk ofcontamination for the container exterior.

The invention also relates to an apparatus for loading the containerswith fuel rods or sections of individual fuel rods of irradiated nuclearreactor fuel elements in accordance with the method of the invention.This apparatus includes a loading trough which is horizontally arrangedand is insertable into a loading aperture in the end wall of thecontainer for pushing the fuel rods or fuel-rod sections into thecontainer. The loading trough is rotatable about its longitudinal axis.

The fuel rods or cut fuel-rod sections are loaded into the container viathe loading trough. The loading trough is then rotated so that its openside is face down. The fuel rods or fuel-rod sections drop down onto thecontainer inner wall surface or onto an already existing pile ofpreviously loaded fuel-rod sections. The loading trough is suitablyarranged as closely as possible to the upper inner wall surface of thehorizontally mounted container.

In an advantageous embodiment of the invention, the feed conduitconnects the separating facility for separating the individual fuel rodsfrom the fuel element or the fuel-rod cutting device with the interiorof the container to be loaded so that dust and aerosols developed duringseparation or cutting of the fuel rods are drawn into the container towhich a partial vacuum is applied. As a result, the cell atmosphere isexposed to extremely low amounts of aerosols and fragments of fissilematerial.

Advantageously, separating or cutting the fuel rods and loading thecontainer are performed in separate work chambers. This still furtherreduces the risk of contamination of the outer surface of the container.A container can be loaded through the closable pass-through openings ifthe loading aperture of the container is in alignment with thecorresponding pass-through opening in the ventilation partition wall.

According to another feature of the invention, a filter is mounted inthe container so as to be parallel to the axis of the container. Thefilter permits filtered air to flow out from the container duringloading thereof. The aerosol and fissile particles are thereby caused toremain in the container.

According to still another feature of the invention, fuel rods areseparated or cut as well as fed and loaded in the presence of aprotective gas. The oxygen-deficient atmosphere thereby obtainedprevents self-ignition of the developing dust.

Also, the container is charged with a test gas so that the loadedcontainer can be tested for leaks in follow-on handling steps.

The invention permits loading separated fuel rods of irradiated nuclearreactor fuel elements as whole fuel rods or as cut up fuel-rod segmentsinto containers in an orderly manner for subsequent interim or terminalstorage. The invention allows a high loading density with a very smallloading aperture. This feature already contributes to reduce the risk ofcontamination of the outer surface of the container. Further embodimentsof the invention almost entirely prevent contamination of the outersurface of the container and permit the various method steps such asseparating, cutting, feeding and loading to be performed in a cleanmanner because, with the further embodiments of the invention, theaerosols and fissile material fragments developed in these steps aredrawn into the container to be loaded in an extremely advantageousmanner.

The invention described solves the engineering problem of loading acontainer with fuel rods or fuel-rod sections.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described in more detail with reference to thedrawing. For better clarity, devices not essential for the understandingof the invention are not illustrated. In the drawing:

FIG. 1 is a schematic of an apparatus for loading fuel-rod sections,with a container shown as it is being loaded;

FIG. 2 is a schematic cross-sectional view of the container to beloaded;

FIG. 3 is a schematic cross-sectional view of the container of FIG. 2showing the loading trough rotated for dropping a fuel-rod section;

FIGS. 4 to 9 are views of the loading aperture in the container as wellas of the feed opening in the ventilation partition wall at variousstages of loading;

FIG. 10 is a view of the filter arranged in the container and shows anarrangement for connecting it to the air system; and,

FIG. 11 is a view of the coupling end of the filter and its connectionin the ventilation partition wall with the container shown docked to thepartition wall.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

In FIG. 1, a container 21 is horizontally docked to a ventilationpartition wall 23. In this embodiment, the container 21 is in the formof a can which is welded closed after being loaded with fuel-rodsections 25 and is then transferred to a terminal storage container. Thecan or container 21 has a loading aperture 29 in the upper area of itsinner periphery. The loading aperture 29 is located in the end wall 27of the container facing toward the ventilation partition wall 23. Theloading aperture 29 is in alignment with a pass-through opening 31 inthe partition wall 23.

The ventilation partition wall 23 divides the working area into twoseparate rooms or chambers 33 and 35 with each chamber having its ownair system. In chamber 35, the container 21 is handled and loaded.Chamber 33 is exposed to open radioactivity because it receives the fuelrods and accommodates a cutting shear 37 for cutting up the fuel rods 39into fuel-rod sections.

The container 21 is connected via a second coupling 41 with a conduit 43extending through the partition wall 23. In this second coupling 41, anair discharge opening 45 of the container 21 is connectable with eithera partial vacuum source 47 or a pressure source of helium gas 49 via asuitable valve (described in more detail in the following). A filter 51for suspended material is placed ahead of the air discharge opening 45and is located within and extends parallel to the longitudinal axis ofthe container 21. The air discharge opening 45 is likewise arranged veryclose to the outermost inner periphery of the container 21.

A loading trough 53 extends through the loading aperture 29 of thecontainer 21 and continues in a closed feed conduit 55 outside theinterior of the container. A pivot drive 57 is fastened to the feedconduit 55 and is adapted to rotate the latter about its longitudinalaxis. The feed conduit 55 extends up to a stationary overarm 59 of thecutting shear 37. The fuel rods 39 are fed into the cutting shear 37 ina stepwise manner where they are cut into individual sections 25 by avertically movable cutting knife 60.

The cutting shear 37 is connected with a source 65 of inert gas via aconduit 61 and a shutoff valve 63 and is charged with this gas. Thesource of inert gas 65 also communicates with the air system of theinterior of the container 21 via the cutting shear 37 and the feedconduit 55.

The helium gas source 49 is connectable with the interior of thecontainer 21 via another shutoff valve 67 and a rotary slide valve 69.The rotary slide valve 69 has a second output 71 connected with a finefilter 73. The output 75 of fine filter 73 is connected via a shutoffvalve 77 with a compressor 47 for generating a partial vacuum. Theoutput of the compressor 47 is connectable with the cell exhaust airsystem via the conduit 61 and a shutoff valve 79.

It will be seen from FIGS. 2 and 3 that the respective connections forloading and venting the container 21 are located as closely as possibleto the inner periphery of the latter. FIG. 2 shows the loading trough 53as a fuel-rod section 25 is being inserted. Following its insertion, theloading trough 53 is rotated (FIG. 3), causing the fuel-rod section 25to drop down onto the container inner wall surface or onto the alreadyexisting pile of orderly loaded fuel-rod sections 25.

The loading aperture 29 of the container 21 is provided in one of itstwo end walls 27 and sealed by a plug 81 when the container 21 is notconnected (FIG. 4). A guide stub 83 is welded into opening 31 of theventilation partition wall 23. A receiving fixture 84 is snugly seatedin guide stub 83 and has an end extending into the loading and handlingchamber 35. This end has a circular recess 85 the inner diameter ofwhich corresponds to the outer diameter of the sealing plug 81. Aninsert key 86 is rotatably mounted in the receiving fixture 84 and hasan actuating hexagon head 87 at its outer end which is located in theshearing chamber 33. A threaded pin 89 is provided at the end of theinsert key 86 which extends through the ventilation partition wall 23.The outer thread of the threaded pin 89 corresponds to an inner ortapped thread provided in the sealing plug 81 of the loading aperture29. The inner thread is in alignment with the threaded pin 89 when thecontainer 21 is docked to the wall.

As shown in FIG. 5, the threaded pin 89 can threadably engage the innerthread of the sealing plug 81 by actuating the hexagon head 87. Thisstep is performed after the container 21 is docked to the partition wall23 with its end wall 27 in which the loading aperture 29 is provided.

The receiving fixture 84 and the insert key 86 are adapted to bewithdrawn from the guide stub 83 as a unit. In this step, with thethreaded pin 89 threadably engaged with the plug 81, the plug 81 ispulled into the shearing chamber 33 through the guide stub 83. Thesurface of the sealing plug 81 remains in the recess 85 of receivingfixture 84 and is thus protected against contamination in the shearingchamber 33. The loading aperture 29 is now clear (FIG. 6).

A feed conduit guide 91 (FIG. 7) through which the feed conduit 55 isintroduced into the container 21 is insertable into the guide stub 83.

The second coupling 41 (FIGS. 10 and 11) includes a second pass-throughopening 93 in the partition wall 23. Opening 93 is in alignment with theadjacent air discharge opening 45 of the container 21 when the containeris docked. A receiving stub 95 is welded into the opening 93. Thereceiving stub 95 has an inner peripheral abutment surface 97 for abearing member 99 with a spherically-shaped outer surface. The bearingmember 99 is pressed against the surface 97 by a nut 101. Bearing member99 and nut 101 have center bores for receiving a coupling member 103therein which, in turn, has an axially parallel inner bore. The couplingmember 103 is loaded in the direction of the container 21 by a pressurespring 105. The coupling member 103 is fixedly attached to conduit 43which includes a flexible compensating member (not shown) to permit anaxial movement of the coupling member 103.

A valve 107 is seated in the aligned air discharge opening 45 of thecontainer 21. The valve cone 109 is loaded by a pressure spring 111which is supported on an end piece 113 of the filter 51. The filter 51is arranged in the container 21 so that its longitudinal axis isparallel to the longitudinal axis of the container. The valve housing115 surrounds the air discharge opening 45 and forms a valve seat 117.The valve cone 109 has an outwardly projecting lug 119 adapted to beacted upon by a lug 121 of the coupling member 103 in the partition wall23. With the container 21 docked to the partition wall 23, the couplingmember 103 lifts the valve cone 109 clear of its valve seat 117 (FIG.11). The spring loading the coupling member 103 and the mounting of thelatter to permit swivelling thereof help to compensate for alignmenttolerances.

The mode of operation of the embodiment described above will now bedescribed.

The container 21 to be loaded is supplied with the loading aperture 29sealed. The container 21 is placed horizontally against the verticalpartition wall 23 so that its end wall in which the loading aperture 29is located faces the wall 23. The loading aperture 29 is tightly sealedby the plug 81 and the pass-through opening 31 in the partition wall 23is tightly closed by the receiving fixture 84 and the insert key 86(FIG. 4).

Also, in the second coupling 41, the two openings 45 and 93 which areprovided in the end wall 27 and the partition wall 23, respectively, andwhich will later cooperate, are still in their rest positions. In thisrest position, the valve cone 109 is seated on the valve seat 117thereby closing the air discharge opening 45. The coupling member 103 inthe partition wall 23 is in its position of rest (FIG. 10), and theconduit 43 is closed by means of the rotary slide valve 69.

After the end wall 27 is brought into abutment with the partition wall23 and the openings 29 and 45 in the end wall 27 are in alignment withthe respective openings 31 and 93 in the partition wall 23, the valvecone 109 will be lifted from its valve seat 117 because the lug 121 ofthe spring-loaded coupling member 103 displaces the valve cone 109axially inwardly (FIG. 11).

In the first coupling between the loading aperture 29 and thepass-through 31, the insert key 86 is rotated by actuating the hexagonhead 87 such that the threaded pin 89 threadably engages the innerthread of the sealing plug 81 (FIG. 5). By axially withdrawing theinsert key 86 into the shearing chamber 33, the sealing plug 81 ispulled into the recess 85 of the receiving fixture 84. A furtherwithdrawing movement pulls the insert key 86 out of the guide member 83together with the receiving fixture 84 and the sealing plug 81 heldtherein. In this way, the insert key 86, guide member 83 and sealingplug 81 are pulled into the shearing chamber 33. The loading aperture 29as well as the pass-through opening 31 are clear (FIG. 6).

The feed conduit guide 91 is then inserted into the pass-through opening31. With its forward loading trough 53 first, the feed conduit 55 ispushed into the center bore of the feed conduit guide 91 until theloading trough 53 is completely received in the interior of thecontainer (FIG. 7). The loading trough 53 then extends parallel to thecontainer cylindrical surface over its entire inner length.

Via the second coupling 41, the interior of container 21 is connectedwith the partial vacuum source 47 by rotating the rotary slide valve 69(position as shown in FIG. 1). The container interior is thus exposed toa partial vacuum.

The source of inert gas 65 applies inert gas to the shearing device 37and to the feed conduit 55. This prevents a possible self-ignition ofdust developing during the cutting step. The fuel rods 39 are fed to theshearing device 37 in a stepwise manner. The cut fuel-rod sections 25are thereby automatically pushed along the feed conduit 55 and fed tothe loading trough 53. When a fuel-rod section 25 is completely receivedin the loading trough 53, the pivot drive 57 is actuated to rotate theloading trough 53 by 180°. The fuel-rod section 25 in the trough 53 willthus drop from there down onto the inner wall surface of the containeror, in the further loading process, onto the previously loaded orderlypile of fuel-rod sections 25.

The shearing device 37 and the feeding of the cut fuel-rod sections 25are air sealed relative to the shearing chamber 33, so that the feedconduit 55, as a result of the partial vacuum developed in the container21, conducts aerosols, dust and other particles developed in theshearing process into the interior of the container 21. These aerosolsand solid particles remain in the container 21 since they are retainedthere by the filter 51 which is inserted ahead of the air dischargeopening 45. Thus, after being fully loaded, the container 21 containsnot only the fuel-rod sections 25 but also, in a most advantageousmanner, the radioactive aerosols and dust particles. The filter 51 alsoremains in the container 21.

When the container 21 is loaded with the predetermined quantity offuel-rod sections 25, the feed conduit 55 and the loading trough 53 willbe withdrawn in the direction of the shearing chamber 33. The insert key86 together with the receiving fitting 84 and the threadably engagedsealing plug 81 are inserted into the pass-through opening 31 (FIG. 8).The sealing plug 81 is again threadably fastened in the loading aperture29 thereby closing the latter. The interior of the container continuesto be connected to the partial vacuum source 47.

Then the rotary slide valve 69 is rotated into a position in which thesource of helium gas 49 is connected with the conduit 43 and thus withthe container interior. The vacuum source 47 is thereby disconnected.The interior of the container 21 is sprayed with helium from the heliumgas source 49 in order to permit a subsequent leakage test of the filledand sealed container 21. For a complete sweeping of the container 21with helium, the application of a partial vacuum to the container 21alternates with the application of helium several times; this isaccomplished by suitably rotating the rotary slide valve 69.

Thereafter, the container 21 is moved away from the partition wall 23(FIG. 9). This automatically closes the air discharge opening 45 in thesecond coupling 41 because the valve cone 109 is again urged intoseating engagement with the valve seat 117 by the load of the pressurespring 111 (FIG. 10). The rotary slide valve 69 is rotated to a closedposition.

Loading the container 21 with fuel-rod sections 25 is thus accomplishedwithout the risk of contaminating the outer surface of the container 21.This facilitates the further handling of the filled container 21. Thecontainer 21 is then placed in a terminal storage container and can besent for terminal storage in a mining depot.

It is understood that the foregoing description is that of the preferredembodiments of the invention and that various changes and modificationsmay be made thereto without departing from the spirit and scope of theinvention as defined in the appended claims.

What is claimed is:
 1. In a fuel rod loading system having a containerand an apparatus for loading the container with fuel rods of irradiatednuclear reactor fuel elements, the container having an end wall and afurther wall transverse to and connected to the end wall, the end wallhaving a loading opening formed therein and the container being placedso as to lie in a plane transverse to the end wall during the loadingthereof, the apparatus comprising:trough means for holding the fuel rodto be loaded into the container; said trough means defining alongitudinal axis and being movably mounted so as to be movable in thedirection of said axis through said loading opening and into saidcontainer; and, pivot drive means for rotating said trough means aboutsaid longitudinal axis whereby the fuel rod held therein drops from saidtrough means toward the lower inner wall surface of the further wall ofsaid container.
 2. The apparatus of claim 1, said trough meansincluding: a feed conduit for receiving the fuel rod to be loaded intothe container; and, an elongated trough extending from said feed conduitfor receiving the fuel rod from said feed conduit as the next fuel rodis inserted into said feed conduit, the composite unit of said feedconduit and said elongated trough being movably mounted so as to movesaid elongated trough into said container for unloading the fuel rod insaid trough.
 3. The apparatus of claim 1, comprising cutting means forcutting said fuel rods into fuel-rod sections before the same are fedinto said trough means.
 4. The apparatus of claim 3, comprising: twochambers having respective air systems; and, a ventilation partitionwall for separating said chambers from each other, said partition wallhaving a pass-through opening formed therein, a first one of saidchambers being configured to accommodate said trough means, said pivotdrive means, and said cutting means; whereas, the second one of saidchambers is configured to accommodate said container; said trough meansbeing movably mounted in said first chamber so as to cause the same tomove first through said pass-through opening and then through saidloading opening of said container for loading said container in saidsecond chamber.
 5. The apparatus of claim 4, wherein the container isprovided with a closure plug in said loading opening, said containerbeing docked next to said partition wall so as to cause said loadingopening to be in alignment with said pass-through opening during theprocess of loading said container, said apparatus further comprisingclosure plug removal means for disengaging said plug from said loadingopening and removing the same through said pass-through opening.
 6. Theapparatus of claim 5, said plug being threadably engaged with saidcontainer and having a threaded bore formed therein so as to beengageable from outside the container, said closure plug removal meansbeing mountable in said pass-through opening and including actuablethread means for threadably engaging said plug at said threaded borethereof.
 7. The apparatus of claim 6, said closure plug removal meansfurther comprising: a receiving fixture; an insert key rotatably mountedin said receiving fixture for driving said thread means; said receivingfixture being mountable in said pass-through opening so as to have anend face exposed to said second chamber, said end face having a recessformed therein for receiving said plug when the same is threadablydisengaged from said container, said recess having a diametercorresponding to the diameter of said plug.
 8. The apparatus of claim 5,said trough means including: a feed conduit for receiving the fuel rodto be loaded into the container; and, an elongated trough extending fromsaid feed conduit for receiving the fuel rod from said feed conduit asthe next fuel rod is inserted into said feed conduit, the composite unitof said feed conduit and said elongated trough being movably mounted soas to move said elongated trough into said container for unloading thefuel rod in said trough; said apparatus further comprising a guidemember insertable into said pass-through opening and having a centerbore for accommodating said feed conduit therein when loaded with a fuelrod.
 9. The apparatus of claim 3, said container having an air dischargeopening formed in said end wall and a filter mounted therein in front ofsaid air discharge opening, the apparatus further comprising partialvacuum means communicating with said air discharge opening to develop apartial vacuum in said container whereby radioactive particles generatedin the handling of said fuel rods are drawn into said container throughsaid loading opening and are prevented from leaving said container bysaid filter.
 10. The apparatus of claim 9, comprising: two chambershaving respective air systems; and, a ventilation partition wall forseparating said chambers from each other, said partition wall having apass-through opening formed therein, a first one of said chambers beingconfigured to accommodate said trough means, said pivot drive means, andsaid cutting means; whereas, the second one of said chambers isconfigured to accommodate said container; said trough means beingmovably mounted in said first chamber so as to cause the same to movefirst through said pass-through opening and then through said loadingopening of said container for loading said container in said secondchamber; said partition wall having a second pass-through opening formedtherein and located so as to be in alignment with said air dischargeopening of said container when the latter is docked to said partitionwall, the apparatus further comprising air valve means for opening anair passage between said partial vacuum means and said air dischargeopening, said air valve means including a coupling piece mounted in saidsecond pass-through opening on said partition wall; a valve mounted insaid air discharge opening for coacting with said coupling piece to opensaid valve when said container is docked to said partition wall therebyopening said air passage to said partial vacuum means and subjecting theinterior of said container to a partial vacuum.
 11. The apparatus ofclaim 2, comprising: cutting means for cutting said fuel rods intofuel-rod sections before the same are fed into said feed conduit; and,inert gas supply means for supplying an inert gas to said cutting meansand said feed conduit, said supply means being configured so as to besealed with respect to the ambient.
 12. The apparatus of claim 1, saidcontainer having an air discharge opening formed in said end wall, theapparatus further comprising helium gas supply means, communicating withsaid air discharge opening for supplying helium to the interior of saidcontainer.